There are two distinct tasks in vision or image processing. On the one hand there is the difficult task of image analysis and feature recognition, and on the other there is the less difficult task of computing the 3D world position of the camera given an input image.
In biological vision, these two tasks are intertwined together such that it is difficult to distinguish one from the other. We perceive our position in world coordinates by recognizing and triangulating from features around us. It seems we can not triangulate if we don't identify first the features we triangulate from, and we can't really identify unless we can place a feature somewhere in the 3D world we live in.
Most, if not all, vision systems in prior art are an attempt to implement both tasks in the same system. For instance, reference patent number U.S. Pat. No. 5,801,970 comprises both tasks; reference patent number U.S. Pat. No. 6,704,621 seems to comprise of triangulation alone, but it actually requires recognition of the road.